U.S. patent number 10,473,523 [Application Number 14/438,183] was granted by the patent office on 2019-11-12 for apparatus for illuminating the surface of a material.
This patent grant is currently assigned to PHOENIX CONTACT GMBH & CO KG. The grantee listed for this patent is PHOENIX CONTACT GMBH & CO KG. Invention is credited to Fred Grunert, Fredrik Hailer, Thomas Nimz.
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United States Patent |
10,473,523 |
Grunert , et al. |
November 12, 2019 |
Apparatus for illuminating the surface of a material
Abstract
An apparatus for illuminating the surface of a material,
comprising an illuminating device for illuminating the surface of
the material with a calibrating light, a recording device for
recording a measuring light, emitted by the surface of the material
in response to the calibrating light, and a processor device for
recording the spectral characteristic of the measuring light that
characterizes a diffuse spectral reflectance of the surface of the
material, wherein the illuminating device is configured to generate
an illuminating light for illuminating the surface of the material
that has a spectral characteristic that corresponds to the spectral
characteristic of the measuring light.
Inventors: |
Grunert; Fred (Bad
Klosterlausnitz, DE), Hailer; Fredrik (Weimar,
DE), Nimz; Thomas (Rothenstein, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
PHOENIX CONTACT GMBH & CO KG |
Blomberg |
N/A |
DE |
|
|
Assignee: |
PHOENIX CONTACT GMBH & CO
KG (Blomberg, DE)
|
Family
ID: |
49485717 |
Appl.
No.: |
14/438,183 |
Filed: |
October 23, 2013 |
PCT
Filed: |
October 23, 2013 |
PCT No.: |
PCT/EP2013/072111 |
371(c)(1),(2),(4) Date: |
April 23, 2015 |
PCT
Pub. No.: |
WO2014/067819 |
PCT
Pub. Date: |
May 08, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150285681 A1 |
Oct 8, 2015 |
|
Foreign Application Priority Data
|
|
|
|
|
Oct 31, 2012 [DE] |
|
|
10 2012 110 429 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N
21/8806 (20130101); G01J 3/027 (20130101); G01J
3/0297 (20130101); G01J 3/10 (20130101); G01J
3/42 (20130101); G01N 21/31 (20130101) |
Current International
Class: |
G01J
3/02 (20060101); G01N 21/88 (20060101); G01N
21/31 (20060101); G01J 3/42 (20060101); G01J
3/10 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101072993 |
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Nov 2007 |
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CN |
|
101371114 |
|
Feb 2009 |
|
CN |
|
10241472 |
|
Mar 2004 |
|
DE |
|
08219716 |
|
Aug 1996 |
|
JP |
|
11237344 |
|
Aug 1999 |
|
JP |
|
05332939 |
|
Nov 2013 |
|
JP |
|
WO 2011126112 |
|
Oct 2011 |
|
WO |
|
Other References
International Searching Authority, "International Search Report"
with English translation, issued in connection with application No.
PCT/EP2013/072111, dated Jan. 20, 2014 (5 pages). cited by
applicant.
|
Primary Examiner: Prieto; Violeta A
Attorney, Agent or Firm: Loeb & Loeb LLP
Claims
The invention claimed is:
1. An apparatus for reducing an influence of interfering light to
illuminate a surface of a material with an illuminating light, the
apparatus comprising: a light source configured to illuminate the
surface of the material with a calibrating light, wherein the light
source comprises lighting elements and a sensor, the lighting
elements provided for emitting the calibrating light and the
illuminating light, and the sensor provided for recording the light
generated by the lighting elements as actual light; a detector
configured to record a measuring light emitted by the surface of
the material in response to the calibrating light and in the
presence of interfering light; and a processor configured to: cause
the detector to record a spectral characteristic of the measuring
light, which characterizes a spectral remission behavior of the
surface of the material; cause the light source to generate the
illuminating light for illuminating the surface of the material in
the presence of the interfering light after recording the spectral
characteristic of the measuring light, automatically adjust the
spectral characteristic of the illuminating light in dependence of
the spectral characteristic of the measuring light recorded by the
detector; wherein the spectral characteristic of the illuminating
light corresponds to the spectral characteristic of the measuring
light, and the interfering light is ambient light, which originates
from outside of the apparatus; wherein the processor is configured
to obtain a measurement signal from the sensor, the measurement
signal including an actual illumination signal, and wherein the
processor comprises a controller to adjust the lighting elements in
the case of a deviation from a desired illumination signal and the
actual illumination signal.
2. The apparatus according to claim 1, wherein the measuring light
is a light reflected on the surface of the material in response to
the calibrating light, or a light reemitted by the surface of the
material in response to the calibrating light, or a light emitted
by the surface of the material in response to the calibrating
light.
3. The apparatus according to claim 1, wherein the spectral
characteristic of the measuring light is a color spectrum of the
measuring light according to a color space, a wavelength spectrum
of the measuring light, or a frequency spectrum of the measuring
light.
4. The apparatus according to claim 1, wherein the light source is
configured to generate the illuminating light with a spectral
characteristic that corresponds to, in particular is equal to, the
spectral characteristic of the measuring light within a tolerance
range.
5. The apparatus according to claim 1, wherein the processor is
configured to transfer an indication on the spectral characteristic
of the measuring light to the light source.
6. The apparatus according to claim 1, wherein the light source
emits the calibrating light in a first wavelength and the
illuminating light in a second wavelength.
7. The apparatus according to claim 1, wherein the lighting
elements are light emitting diodes.
8. The apparatus according to claim 1, wherein the light source is
configured to control at least one light element of the lighting
elements, in particular each light element of the lighting
elements, for emitting light of a predetermined intensity, in order
to adjust the spectral characteristic of the illuminating
light.
9. The apparatus according to claim 1, wherein the processor is
configured to record a characteristic of the surface of the
material on the basis of the measuring light.
10. The apparatus according to claim 1, wherein the detector
comprises an optical sensor for recording the measuring light.
11. The apparatus according to claim 1, wherein the processor is
further configured to record a difference between a spectral
characteristic of the actual illuminating light and a spectral
characteristic of a desired illuminating light, and is further
configured to control the light source in dependence of the
difference.
12. The apparatus according to claim 1, wherein the detector is
configured to record an image light emitted by the surface of the
material in response to the illuminating light.
13. The apparatus according to claim 12, wherein the processor is
further configured to convert the image light into a test
image.
14. A method for reducing an influence of interfering light to
illuminate a surface of a material with an illuminating light, the
method comprising: illuminating the surface of the material with a
calibrating light; recording a measuring light emitted by the
surface of the material in response to the calibrating light and in
the presence of interfering light; recording a spectral
characteristic of the measuring light, which characterizes a
spectral remission behavior of the surface of the material;
automatically adjusting the spectral characteristic of the
illuminating light in dependence of the recorded spectral
characteristic of the measuring light; illuminating the surface of
the material with the illuminating light in the presence of
interfering light after recording the spectral characteristic of
the measuring light, the illuminating light having a spectral
characteristic that corresponds to the spectral characteristic of
the measuring light, wherein the interfering light is ambient
light, which originates from outside of an apparatus for
illuminating the surface of the material in accordance with the
method; obtaining a measurement signal from a sensor recording the
illuminating light, which represents an actual illumination signal;
and adjusting the illuminating light in the case of a deviation
from a desired illumination signal and the actual illumination
signal.
Description
FIELD OF THE INVENTION
The present invention relates to the field of illuminating objects
such as, for example, workpieces, for the optical detection of
object detection.
RELATED TECHNOLOGY
In modern manufacturing installations, there is often the need for
optical recording or detection of objects such as, for example,
workpieces, products and the like. For this purpose, the surfaces
of objects are usually illuminated with white light, wherein the
light that is reflected by the surface of an object is optically
recorded and optionally further conditioned in order to obtain an
image of the object.
However, the optical recording and the analysis of the optically
recorded image of the object can be disturbed by interfering light,
for example, by ambient light such as hall illumination or by
scattered light.
For this reason, there is a need to reduce the influence of
interfering light in the optical recording of objects, particularly
in manufacturing installations.
For this purpose it is indeed possible to increase the intensity of
the object illumination. However, this can lead to the generation
of additional interfering light, which can disturb, for example,
adjacent optical recording operations. Another possibility for
reducing the influence of the interfering light consists in
optically recording the interfering light and reducing the
intensity of the object illumination in the spectral range of the
interfering light, in order to obtain a homogeneous illumination of
the object. However, this is problematic particularly if the
spectral intensity pattern of the interfering light is subject to
temporal variations, which is the case, for example, with
artificial illumination or at different times of the day.
SUMMARY
Therefore, the object of the present invention is to create an
efficient concept for the illumination of surfaces of materials,
wherein the influence of interfering light can be reduced.
This object is solved by the features of the independent claims.
Advantageous variants are subject matter of the description, the
drawings as well as the dependent claims.
The present invention is based on the finding that the above object
can be solved by an adaptation of an illuminating light that is to
be used for illuminating a surface of a material, for example, a
surface of a workpiece.
For this purpose, the surface of the material is illuminated at
least twice, wherein, in a first illumination process, the spectral
remission behavior of the surface of the material is recorded. The
spectral remission behavior of the surface of the material, which
is characterized by a measuring light coming from the surface of
the material, is used in order to adapt the illuminating light or
the spectral characteristic thereof, in particular the color
temperature, to the measuring light.
In this manner, the spectrum or the color composition of the
illuminating light to be used for illuminating the surface of the
material is adapted to the optical properties of the surface of the
material. If the surface of the material is characterized, for
example, by a stronger intensity of the reflected light in a first
spectral range than in a second spectral range, then the intensity
of the illuminating light in the first spectral range can be higher
than the intensity of the illuminating light in the second spectral
range. In this manner, the surface of the material is spectrally
illuminated with a greater intensity at the site where a stronger
response intensity should be expected. On the other hand, if the
surface of the material absorbs light of a certain wavelength, then
it is possible, for example, to dispense with the illumination of
the surface of the material at this wavelength. This leads to a
more energy-efficient illumination of surfaces of materials.
According to one aspect, the invention relates to an apparatus for
illuminating a surface of a material, comprising an illuminating
device for illuminating the surface of the material by means of a
calibrating light, a recording device for recording a measuring
light emitted by the surface of the material in response to the
calibrating light, and a processor device for recording the
spectral characteristic of the measuring light, which characterizes
a spectral remission behavior of the surface of the material;
wherein the illuminating device is configured to generate an
illuminating light for illuminating the surface of the material,
which has a spectral characteristic that corresponds to the
spectral characteristic of the measuring light.
According to an implementation form, the measuring light is a light
reflected on the surface of the material in response to the
calibrating light, or a light reemitted by the surface of the
material in response to the calibrating light, or a light emitted
by the surface of the material in response to the calibrating
light.
According to an implementation form, the spectral characteristic of
the measuring light is a color spectrum of the measuring light in
accordance with a color space, a wavelength spectrum of the
measuring light, or a frequency spectrum of the measuring
light.
According to an implementation form, the illuminating device is
configured to generate the illuminating light with a spectral
characteristic that corresponds to, in particular is equal to, the
spectral characteristic of the measuring light within a tolerance
range, for example, 1%, 5% or 10%.
According to an implementation form, the processor device is
configured to transfer an indication on the spectral characteristic
of the measuring light to the illuminating device. As a result, the
illuminating device can be controlled, for example, so as to
generate the desired illuminating light.
According to an implementation form, the processor device is
configured to control the illuminating device for adjusting the
spectral characteristic of the illuminating light in dependence of
the spectral characteristic, in particular in accordance with the
spectral characteristic, of the measuring light.
According to an implementation form, the illuminating device
comprises a plurality of light elements for emitting light of
different wavelengths or different colors.
According to an implementation form, the illuminating device is
configured to control at least one light element of the plurality
of light elements, in particular each light element of the
plurality of light elements, for emitting light of a predetermined
intensity, in order to adjust the spectral characteristic of the
illuminating light.
According to an implementation form, the processor device is
configured to record a characteristic of the surface of the
material on the basis of the measuring light.
According to an implementation form, the recording device comprises
an optical sensor for recording the measuring light.
According to an implementation form, the illuminating device
comprises an optical sensor for recording an actual illuminating
light, wherein the processor device is configured to record a
difference between a spectral characteristic of the actual
illuminating light and a spectral characteristic of a desired
illuminating light, and to control the illuminating device in
dependence of the difference. As a result, the illuminating light
can be adjusted with automatic control.
According to an implementation form, the recording device is
configured to record an image light emitted by the surface of the
material in response to the illuminating light.
According to an implementation form, the processor device is
configured to convert the image light into a test image, in
particular into a digital test image.
According to an additional aspect, the invention relates to a
method for illuminating a surface of a material, with an
illumination of the surface of a material with the calibrating
light, a recording of a measuring light emitted by the surface of
the material in response to the calibrating light, which
characterizes a spectral remission behavior of the surface of the
material, a recording of a spectral characteristic of the measuring
light, and an illumination of the surface a material with an
illuminating light which has a spectral characteristic that
corresponds to the spectral characteristic of the measuring
light.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional implementation forms are described in reference to FIG.
1, which shows a block diagram of an apparatus for illuminating a
surface of the material.
DETAILED DESCRIPTION
FIG. 1 shows a block diagram of an apparatus for illuminating a
surface of the material 103, with an illuminating device 101 for
illuminating the surface of the material 103 by means of a
calibrating light 105, and with a recording device 107 for
recording a measuring light 109 emitted by the surface of the
material 103 in response to the calibrating light 105. The
measuring light can be, for example, light reflected on the surface
of the material 103 or light emitted or reemitted by the surface of
the material 103.
Furthermore, a processor device 111 is provided, which is
configured to record a spectral characteristic, for example, a
color composition or a wavelength pattern, of the measuring light
109. The spectral characteristic of the measuring light 109
characterizes, in particular, the spectral remission behavior of
the surface of the material. The measuring light can be, for
example, reflected light, reemitted light or emitted light.
The illuminating device 101 is configured to generate an
illuminating light 113 for illuminating the surface of the
material, which has a spectral characteristic that corresponds to
the spectral characteristic of the measuring light.
The illuminating process is thus a two-step process. In the first
step, the illuminating device 101 generates the measuring light
105. After the recording of the spectral characteristic of the
measuring light 105, the surface of the material 103 is illuminated
with an illuminating light 113 whose spectrum corresponds to the
spectrum of the measuring light, within a tolerance, for example,
5% or 10%. Therefore, the measuring light 105 is generated first.
The illuminating light 113 is generated temporally after the
generation of the measuring light 105.
The illuminating device 101 comprises a plurality of light elements
115, which are provided for emitting the calibrating light and/or
the illuminating light. The light elements 115 can be, for example,
light emitting diodes (LED), each of which emits light of a
different color, for example, red, green or yellow, or of another
wavelength. By energizing the individual light elements 115, a
predetermined color composition or spectral characteristic of the
illuminating light can be generated.
An optics unit 117, for example, a lens, can optionally be
connected downstream of the light elements 115, for example, in
order to focus the emitted light.
For driving the light elements 115, a driver 119, for example, an
LED driver, is provided, which is connected upstream of the light
elements 115.
According to an implementation form, the driver 119 is an element
of the illuminating device 101. According to another implementation
form, the driver 119 is an element of the processor device 111.
The illuminating device 101 comprises a sensor 121 which is
provided for recording the light generated by the lighting elements
115, optionally after the optics unit 117, as actual light, in
particular as actual illuminating light, and for applying a
corresponding measurement signal to the processor device 111 for
the automatic control of the control system of the illuminating
device 101.
The illuminating device 101 is provided in order to emit, by means
of the lighting elements 115, both the calibrating light 105, for
the calibration of the system to the surface of the material, and
also the illuminating light 113 in the direction of the surface of
the material 103, which characterizes the spectral light behavior
of the surface of the material.
The light emitted or reflected by the surface of the material 103
in response to the calibrating light or illuminating light is
recorded by the recording device 107. For this purpose, the
recording device 107 comprises an optical sensor 123, which
optically records the light 109 emitted by the surface of the
material 103. An output signal of the optical sensor 123 is applied
to a control unit 125.
In accordance with an implementation form, the control unit 125 is
an element of the recording device 107. According to another
implementation form, the control unit 125 is an element of the
processor device 111.
The control unit 125 comprises an interface 127 which can be
digital and which can be configured, for example, as a 120, SPI,
USB or a similar interface.
The interface 127 can comprise an analog-digital converter, for
example. This is advantageous if the optical sensor 123 converts
the recorded light into an analog measurement signal. If the
optical sensor 123 is provided in order to convert the recorded
light into a digital signal, then the interface 127 can be an I2C,
SP or a USB interface, for example.
Arranged downstream of the interface 127 is a signal conditioning
device 129 which carries out, for example, a filtering of an output
signal of the interface 127. The filtering can produce, for
example, a signal smoothing. The signal smoothing can be dependent
on a frequency or wavelength of the recorded or measured light.
The control unit 125 moreover comprises an optional calibration
device 130 which is provided in order to receive the conditioned
signal data from the signal conditioning device 129 and calibrate
the data. Here, the conditioned signal data can be calibrated, for
example, in terms of the color value according to a color
space.
The output data of the calibration device 130 can be applied
according to an implementation form to the processor device 111, in
particular to an automatic control device 131 of the processor
device 111.
According to an implementation form, the output data of the
calibration device 130 can be applied to an optional decision
device 133.
According to an implementation form, the decision device 133 can
perform, for example, an edge detection in a digital image, for
example, in order to detect contours of the illuminated object with
the material surface.
According to an implementation form, the decision device 133 can
associate the spectral characteristic of the light, which is
emitted by the surface of the material 103 in response to the
calibrating light or illuminating light and recorded, with actual
color values, which can define not only the spectral characteristic
of the measuring light, but also the spectral characteristic of the
illuminating light to be used. In this manner, the illuminating
device 101 can be controlled automatically for generating a desired
illuminating light.
For this purpose, the processor device 111 comprises a control unit
137, for example, an LED control unit, which controls the driver
119 in accordance with the desired color values of a desired
illuminating light, for generating an illuminating signal. For this
purpose, the control unit 137 can be configured in order to control
the lighting elements 1115 associated with respective colors, for
example, individually, in order to obtain the spectral
characteristic of the illuminating light in accordance with the
spectral characteristic of the measuring light or the desired color
values.
Optionally, the automatic control device 131 can be provided in
order to adjust the lighting elements 1115 in the case of a
deviation between the desired illuminating signal and an actual
illuminating signal, so that, for example, a difference between the
desired illuminating signal and the actual illuminating signal, in
particular a spectral difference, can be reduced.
For this purpose, the processor device 111 can be configured so as
to obtain a measurement signal from the sensor 121, which
represents the actual illuminating signal. The sensor 121 can be an
optical sensor which converts visible light into an analog or into
a digital measurement signal. The processor device 111 can comprise
an interface 139 for receiving a measurement signal from the sensor
121, interface which can be digital and configured, for example,
which can be digital and which can be configured, for example, as a
120, SPI, USB or as a similar interface.
The interface 139 can comprise, for example, an analog-digital
converter and/or be a 120, SBI or USB interface. Connected
downstream of the interface 139 is an optional signal conditioning
141, which can have the functionality of the signal conditioning
129 of the control unit 125. The signal conditioning 129 can
perform, for example, a signal smoothing, for example, in
dependence of a frequency of the measured light.
An optional calibration device 143, which carries out a correction
of the conditioned signal data in terms of color value, is
connected downstream of the signal conditioning device 141. The
calibration device 143 can have the functionality of the
calibration device 130. The calibration device 143 is provided, in
particular, for applying an actual color value, which characterizes
the spectral characteristic of the actual illuminating signal, to
the automatic control device 131. The automatic control device 131
is configured, for example, to determine a deviation between the
actual color value and the desired color value, and to issue, on
this basis, an actuating variable for the control unit 137, in
order to control the driver 119 for driving the lighting elements
115.
According to an implementation form, the control unit 137, the
interface 139, the signal conditioning device 141, the calibration
device 143 as well as the automatic control device 131 can be
implemented by means of a microcontroller.
LIST OF REFERENCE NUMERALS
101 Illuminating device 103 Surface of the material 105 Calibrating
light 107 Recording device 109 Measuring light 111 Processor device
113 Illuminating light 115 Light element 117 Optics 119 Driver 121
Optical sensor 123 Optical sensor 125 Control unit 127 Interface
129 Signal conditioning device 130 Calibration device 131 Automatic
control device 133 Decision device 135 Display 137 Control unit 139
Interface 1115 Lighting element 141 Signal conditioning 143
Calibration device
* * * * *